(1) Field of the Invention
This invention relates to submarine ejection systems, and is directed more particularly to a valve assembly for use therein.
(2) Description of the Prior Art
Prior art submarine ejection systems for launching devices, such as countermeasures or signal buoys, utilize a component which senses depth of the submarine. In response to the determined depth, pneumatic pressure in the ejection system is increased to a selected increment higher than the sea pressure at the determined depth. To accomplish ejection, high pressure air is ported to an ejection cylinder in which is disposed a piston which receives the high pressure air on one side thereof and moves in the cylinder to expel sea water on the other side thereof from the cylinder. The expelled water is ported to the breech of a launch tube. Inasmuch as the expelled water is at a higher pressure than outside sea pressure, a pressure differential occurs between the breech and muzzle ends of the device within the launch tube, launching the device from the tube.
Systems as described above suffer two disadvantages. Firstly, depth sensing and pressure compensation systems are not always reliable; and, secondly, bringing the high pressure air up to an appropriate pressure and rapidly releasing it results in a significant noise signature. As a submarine goes to deeper depths, higher air pressures are required to compensate for the deeper depth. The energy expended to obtain the air pressure required for deeper depths produces undesirable noise.
Recently proposed systems overcome the above-noted two disadvantages. The depth compensation system may be eliminated by utilizing a launch system, the operation of which is relatively independent from the depth of the submarine. This is accomplished by connecting a water cylinder/piston with an air cylinder/piston, via a common shaft. As ejection air is ported into one side of the air piston, water is forced from one side of the water piston into the launch tube. As the water piston moves in a direction which forces water into the launch tube, water is drawn from sea to backfill the void which is created by the moving piston. As both sides of the water piston are subjected to sea pressure prior to, during, and following launch, the energy required to launch a device is proportional to the overpressure needed for device ejection and independent from sea pressure. As a fixed amount of energy is required to launch a device, regardless of the submarine depth, the launch system may have a minimal launch signature. The only disadvantage to this system is that a separate sea water feed must be provided to the water piston as it moves in a direction to effect a launch. This requires a separate hull penetration for each launch system utilized. One solution is to provide only one ejection system for two launch tubes. While this minimizes the number of hull penetrations required, it slows the rate at which one ejector can be fired after another, as the launch piston assembly must be returned to its at-battery position before it can be fired a second time.
A number of alternative launch systems have been proposed which may, in due course, replace the ram-pump system above described. These systems include an elastomeric bladder ejection system, an electromagnetic ejection system and a rotary pump ejection system. All these systems have the common characteristic of being pressure balanced and all require a separate hull penetration to back feed sea water which is displaced to effect a launch.
There is, therefore, a need for a submarine balanced ejection system valve assembly which will facilitate the use of one ejection system for two launch tubes, without the penalty of slow sequential launches from the two tubes and without requiring an additional hull penetration.